Pen



FIG. 1 is a front view of the invention;

FIG. 2 is a right side view of the invention;

FIG. 3 is a rear view of the invention;

FIG. 4 is a left side view of the invention;

FIG. 5 is a perspective view of the invention;

FIG. 6 is a bottom view of the invention; and,

FIG. 7 is a top view of the invention. 

The ornamental design for a pen, as shown and described. 